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Oct. 30,1951 w. E LiMACG EORGE RELAY Original Filed April 9, 1947 2SHEETS-SHEET 1 LOAD V D D D T 5. INVE/V TOR MAL/AM 0 MACGEa/PGZ' ATTO/PNE Y5 Reissued Oct. 30, 1951 23,426 I RELAY William D. Macgeorge,Collegeville, Pa., assignor to Automatic Temperature Control 00., Inc.,

Philadelphia, Pa., a corporation of Pennsylvania Original No. 2,554,467,dated May 22, 1951, Serial No. 740,507, April 9, 1947.

Application for reissue August 9, 1951, Serial No. 241,137

Claims.

Matter enclosed in heavy brackets I: appears in the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

This invention relates to relays, and particularly to relays oftriggtr"action, operative, for instance, upon the attainment of adesired condition of a conditioned device.

There are many situations in the industrial arts in which thevariationlis] of a given condition is manifested by the minute movementof an associated element and in which therefore its instantaneousposition is a function of the condition of the device. It is frequentlydesired that the attainment of a'predetermined condition of such devicebe used as a control function, whereby some collateral or relatedactivity is started, terminated or modulated. A typical illustration iscomprised by a weighing beam, the attitude or position of which changeswith the gradual addition of weight to the weighing hopper or platform,and by which it is desired to shut off or otherwise regulate the inflowto the platform or hopper of the weighing device when the desired amountof the articles has been deposited thereon from 'some automaticallycontrollable supply. The weighing beam is, of course, a purelyillustrative example, and any other condition than weight may besimilarly controlled or used as a collateral controlling device, or anymovable element responding to changes of condition of a conditioneddevice can be used, whether the condition be temperature, pressure,weight, humidity, fluid flow rate, liquid level indication, orotherwise, the attainment of a predetermined condition is used as themeans for either signalling the fact, or controlling some elementaffecting the condition or for other purposes.

There may also be desired two different types of control functions,depending upon the condition to be controlled. In one case, as in theweighing beam used as an illustration, it may be desired to effect atrigger action relay actuation in one sense only, as by the start of aload circuit such as will shut off the supply through suitable motormeans or the like. In the other type of conditioned device control itmay be desired to actuate two different load circuits in alternation oneach side of a predetermined null point, such, for instance, as twovalves or the like controlling the rate of flow in a flow meter, inwhich one valve is caused to have one operating positioning during apredetermined minimum flow, to be controlled and stopped in itsoperation when the rate of flow reaches a predetermined point, followedby the controlled action of another valve when'the rate of flow exceedsthe predetermined given rate. More simply, the alternative load circuitsto be controlled may be represented by two signal devices,

one functioning when the rate is below the predetermined rate, bothsignals to have the same indication or lack of it when the flow attainsthe predetermined given rate, and the other signal to function when therate exceeds the predetermined given rate.

There have been several attempts to provide a solution to the problem,but so far as known such other efforts have involved complicated andexpensive installations, and in many cases have by their very presenceeffected a modification of the apparent condition, to the nullificationof the'extreme accuracy that is so frequently desired.

It is among the objects of this invention: to improve the art of relays;to obviate the disadvantages of prior art relay structures andinstallations; to provide a trigger-action relay system having oneelement positionable as a function of condition of a conditioned devicewhile the remainder of the system is a self-contained unit;

to provide a trigger-action relay having a movable portion which is ofinappreciable affect so far as effecting a modification of the conditionindication; to provide a relay responsive of itself to the truecondition of a conditioned device; to provide a trigger-action relay susceptible to facile and'accurate adjustments to vary the condition atwhich the trigger-action relay functions; to provide a trigger-actionrelay system sensitive to minute mechanical displacements of its primaryelement; to make a differential transformer arranged to effect acontrolled output responsive to wide mechanical displacements; toprovide a relay system incorporating a differential transformer, themovable armature of which is arranged to move as a function of aconditioned device, in which the differential transformer is adjustablerelative to the armature to preselect the range of operation of thearmature; to provide a diiferential transformer with an operatingcontrol system in which the functioning of the system is responsiveselectively to unbalance of the transformer in one sense, to theattainment of a null point of output from the transformer, and to theattainment of unbalance of the transformer in the opposite sense; toprovide a.relay system for operation with a movable armature of adifferential transformer having a null point between outputs of oppositesenses as functions of position of the armature, in which the range ofmovement of the armature during the null point is predeterminedlyvariable; and to provide other objects and advantages as will becomemore apparent as the description proceeds.

In the accompanying drawings forming part of this description:

Fig. 1 represents a diagram of one illustrative circuit of the relay ofthis invention operatively associated with a movable element whichchanges position or attitude in accordance with the change in conditionof a conditioned 'devica; and in which the relay disclosedrespondstochanges in position of the armature as small as .0002 inch. I

Fig. 2 represents a diagram of another-illus trative circuit of therelay of this invention'inr which two alternative load circuits arecontrolled as functions of the position of the armature associated-witha movabl element of a conditioned device relative .toaa: differentialtransformer, having a null point of variable length.

Fig. 3 represents a side elevation, and Fig. 4 represents a transversesection, of an illustrative mounting for the differential transformerrelative to the movable element of the conditioned device topredetermine the range at which'the critfcal'functioning of thetransformer is main fested.

Referring to the form of the device shown in Fig. l, a movableelement,,such as a lever arm II! is provided, which, illustratively,moves substan tially'verticall y, ,as a functionof change of thecondition of a conditioned device, and for purposes of illustration-Wi11 be deemed a weighing beam or arm, which, with no load on the beam,is at a low point, and with increase of load on the platform or hopperthereof-moves upwardly. It is desired to actuate the relay at apredetermined poi'nt'in this travel corresponding to the disposition ofa predetermined weight on the scale. Tied to or actuated by the end'ofthe arm is a movable armature or magnetic core .I I, which is displacedvertically, preferably. by risinglfrom a low starting position, as theload'is' appliedto the weighing device. The'armature II is guided tomove vertically through and relative to a differential transformer! 2,of the relay. circuit to be described and is substantially separatedfrom the stator coils tofper'clude] preclude the possibility of 'anyfriction'dra'gi The transformer IZ'comprises, il

lustratively, upper and lower oppositely wound series'connectedsecondarycoils I3and I4, energized by'the alignedmedian primary coil I5"disposedsymmetrically" between coils I3' and" IE. The secondarycoils"arecoupledin opposition and have "outputs of op'po'sit'e phase so as to mutuallycancel each other when the armature l I is exactly"centered inth'eexciting 'coil" IS, or'to' have a preponderating voltageand phasein onephase A or the'oth'er'ph'ase B, according to whether" the" asymmetricaldisposition" of" the armature is toward coil I3 or -I4. The output ofcoils I3 and-- I 4 passes" through" the primary l E of a transformer IT;The'se'con'dary I8"of transformer I'I connects at'one"'endto" the gridofa preferably, althou'gh'not" necessarily, gas filled tube 20,- andtheother'endconn'ects tothe mov-' able arm of a p'otentiomet'enfl'inthecath-ode circuit. The cath'odeis energized by secondary turns 22*of apower transformer 23"; the primary 2 10f which is in'the power lineLi-L'z. The sec ondary turns" 22"of"the power transformer are connectedto the primary. coil I5 of the differential transformer I2" as aconstantexciting. source therefor. The other secondary 2910f"transformer 2'3'is in the cathode-anode circuit, and includes acontrollingrelay 2 5 which when energized, either closes or opens theswitch 26in the load circuit'I- -2, dependingv tion desired.

It will be observed that adjustment of the potentiometer 2| varies thegrid bias of the tube 20,

. and this adjustment is coordinated with the conditionof the device,indicated by the position or attitude of -the movable arm ID, todetermine the trigger-conditionat'which the relay 25 is to be energized,to close-.(or, as the case may be, to open) the loadlcircuit, andthusdirectly or indirectly toocontrol the condition or sound or cuit iscoupled to automatic means for shutting,-

off or interrupting the supply of weightto the weighing arm, so thatwhen the predetermined weightis applied to the scale, the supplyisinstantly terminated by the' action ofswitch" 26 controlled by. relay.25L' Obviously, it can equally}.

well be used to shut-off or open any desired valve, damper, electricsupply, fuel'or energy flow or otherwise, or to actuate a signal.

It'will be understood that the coils I3 and M as stated are woundoppositely, the, inducedvoltage in the respective coils will'result in anull output when the armature II is centered' in the median primarycoil"'l5symmetrically of the end turns I3 and I4 dueto mutualcancellation. It will be understood as explained thatth'e positioning ofthe armature I I slightly. asymmetricallyin the primary coil I5 willinduce a higher voltage of one phase in one coil, of the coils I3 andI4, than the voltage and opposite phase in the other, and therefore inaccordance with the direction of asymmetry there will be apreponderating voltage and phase in one coil of coils I3and I4, with anoutput through the primary IE of the transformer I! in accordance withsuch preponderating voltage. With a predetermined. bias on the tube, it

will be seen that with proper circuit connections and with the. armatureII in the lower secondary coil I4, the initial output of thedifferential transformer will be a voltage of a phase such as to augmentthe bias of thetubeatthe inception cithe control motion, which precludesany transmission through. the. tube. With upward movement. of armature Il and decrease of the value of the-preponderating voltage, the grid biasaugmentation progressively diminishes, until the critical range of thecircuit is reached. This =begins-whenthe vertical progress of thearmature. has caused it to reach a point of symmetry-in the-diiferentialtransformer, at which theoutput of the transformer I1 is null, andends-When withslightfurther upward movement of the armaturethere-is areversal ofth'e-preponderating: voltage: in the transformer H; at which,with. proper [polarity] phase and increasing voltage the output of thetransformer balances and. thentovercomes the bias on the tube, at.whichpoint the tubefi-res or is energized tocause flow in the. anode;circuit; the switchleof relay 25-is pulled/in. orout and the loadcircuitis instantaneously con-trolled.

It willbe understood thattthe potentiometer is calibrated in terms ofcondition, so that the applied variable bias is set forthe:trigger-action ofthe relay at the desired point ofchange incondition, as illustratively manifested by the vertical positioningl of.the 1. armature, following the movement of the arm I 0. Thispotentiometer .upon the controlling accated in Figs. 3 and 4.

5 is used as a Vernier setting only, all major adjustments beingaccomplished by mechanically altering the relative positions of thedifferential transformer stator and armature. This insures that relayaction will occur only when the differential transformer armature isrelatively close to-null position, where little or no reactive-forcewill be transmitted back to the conditioningde- Vice. 1 7 A V Forpurposes of adjustably mounting the differential transformer relative tothe movable armature, some such device can be used as indi In this moreor less schematic disclosure, the transformer I2 is mounted on a plate30, of preferably non-inductive material, and is slidably guided in afixed guide 3|, having the vertical groove or recess 32 to receive andguide the plate, and one edge of the guide is suitably calibrated as at33, for selective registration by a pointer or the like 34, carried bythe transformer l2 or its-supporting plate 30. It will be seen that withthe guide fixed generally vertically above or below the movable elementof the conditioned device, the transformer can be adjusted with easerelative to the armature ll so as to vary the critical point of thejuxtaposed armature and transformer. The form of differentialtransformer disclosed is preferred under certain conditions, but isillustrative of a transformer, the output of which varies between onephase of voltage output, a null point of no output, and a substantiallyopposite phase of voltage output according to the positioning of thearmature relative to the transformer, and other forms of differentialtransformers having similar characteristics can be used, either with theform of relay circuit shown in Fig. 1, or that shown in Fig. 2.

Referring to the latter figure, a circuit is dis closed in which theoutput of the differential transformer is from leads 35 and 36, of whichlead 35 is also common with one line of the primary coil [5, and whichleads are joined in the primary 3! of a transformer 38. Primary coil I5is fed by the secondary of a power transformer 46, the primary '45 ofwhich is connected to line connections L1 and L2. Two tubes,respectively 40 and 4|, which illustratively may comprise G. L. 502Atubes, are provided, the grids of which are coupled to therespectiveends of center tapped secondary 42 of the transformer 38. Thecenter tap connection of the secondary 4-2 leads to the potentiometerarm 43 of the potentiometer -44 by which the tubes are both given anegative grid bias, variable with settings of'the potentiometer. Thepower lines L1 and L2, as noted, actuate the primary 45 of thetransformer 46, the secondary of which furnishes approximately six voltsfrom which the negative grid bias is applied, and these lines alsofurnish the tube voltages. A normally closed relay 48 is disposed in theplate circuit of the tube 40, and in the normal position of the switch50 of this relay it completes a circuit from one side of the line L1, L2to the normally open switch 5| controlled by the relay 52 in the platecircuit of the tube 4|. Electrical agencies indicated broadly as motors54 and 55 each have one side coupled to the return side of lines L1, L2and their other sides coupled respectively to the abnormally closed sideof switch 59 and to the closed side of normally open switch 5|. It willbe observed that the operation of one tube and its associated relayprecludes simultaneous operation of the agency controlled by the otherrelay, and vice versa.

With the armature 1 I asymmetrically located in the transformer l2,say,-toward the secondary coil [4, of the series connected secondariesI3 and I4, there will be an output through the connectors 35 and 35leading to the primary 3'! of transformer 38, of a voltage, say, of Aphase, and if the voltage is great enough to overcome the presetnegative grid bias, the tube of the two tubes responding in its grid tothe A phase voltage will fire andwill actuate and hold inits-operatively associated relay. Let it be assumed that grid of tube 40respondsto A phase voltage to overcome the bias and fire the tube, whilethe grid of tube 4| responds to B phase voltage for firing the tube. Theelectrical agency 54 will remain actuated so long as the armature isasymmetrical of the differential transformer l2v in a direction such asto produce an output of A phase. As the armature ll moves in response tothe change of condition of the conditioned device, the induced output ofA phase will diminish in voltage until at some point the output willstop and be null. At about this point the bias of .the tube" reassertsitself and the tube stops firing and the relay 48 .drops out. Theelectrical agency 54 which the latter controls will stop, and theoperator, if there is one, will know that the null point has beenreached. When. and if the armature resumes its travel in the samedirection, the null output is rapidly changed to an output of voltage ofB phase,- and whenthis attains sufficient amplitude the voltageimpressed on the grid of tube overcomes the negative grid bias thereonand the tube 41 fires, pulling relay 52 in and closing the circuitthrough the electrical agency 55. It will be seen that adjustment of thepotentiometer varies the degree of biasing of the grid of eachtube, andeffectively lengthens the degree of motion of the armature in thetransformer at which the effective output of the differentialtransformer is at the null point. As both the firing voltage and thebiasing voltage are from the same approximately six volt source, anyfluctuations in the line voltage L1, L2 will be proportional and willnot affect the operation of the system to ,any appreciable degree Itwill be understood that conversely a downward movement of the armaturefrom the upper coil down toward the lower coil of the diiferentialtransformer is available for such triggeraction or successivealternating trigger-action controls. In such case the tube continues tohave an output holding the relay 25 in (or out) in Fig. 1, or eitherrelay of Fig. 2, until with movement of the armature the energization ofthe grid to pass a current is neutralized by the grid bias, at whichinstant the tube ceases to transmit and the previously adjusted relaydrops out.

An important feature of the invention is the fact that although thecurve of the ponderomotive forces of the differential transformer isonly substantially linear in the area adjacent to the median point ofsymmetry of the armature in the primary coil, the resistance to themotion of the armature in the transformer is a minimum at this criticalpoint, so that although at or toward the extreme ends of the maximummotion of the armature the electrical resistance to physical motionmight be such as to effect such a physical drag on the armature as toupset the reading of the weight or other condition, this drag orresistance diminishes and reaches a substantial zero as the armaturereaches the critical symmetrical areag-so tha-tc-the .presencewof thearma- 11111 85011: the beammovingin the differential transformer effectsno change in -the-rreadingi, of..the-

effective weight onthebeam; at least atthe point when; extreme:accuracy: is essential;

The compactness, simplicity, extremely; low? cost and trouble-free.natu-re-of theinvention will: baa-understood.

Having thus described my invention,- 1 claim;

1. A trigger action. relay-circuit: comprising .anarmature: and adifferential transformer, .means for seeuring: .relative movement ofthe5armature. and transformer as:functions ofatheschangeswot.conditionrof aconditioned. device, arela-y circuit. comprising a tube;means for applying a-lnegativeagrid bias to the:tube-, means forconductingthe output ofthedifierential: transformer to the grid. of thetube toenergize thetube; When.the.-.armature is'in one predeterminedrelation .to the trans. former at which the grid bias isbalanced, a,relay. in' the=tube circuit, asecond tubein said..-re1ay circuit, meansfor applying;-avariablernegative grid bias to the said second tube,:mean's..for conducting the outputof the differentialtransformer: to thegridof the second tube. to energize the secondotube whenzthe armatureisin a second predetermined: relation to the. transformer at which thegrid "bias-f the second-tubeis. balanced,. and a second relay: in thesecond. tube. circuit;

2., .A f trigger action relay; circuit. comprising an armatureand; adifferential transformer, means: forzjsecuring relative movement of thearmature and transformer as functions: of the changesof condition ofacondition'eddevice, ai-relay' circuit comprising a tube,,means.forapplying a negative grid, bias :to thetube, means for conducting theoutputof the difierenti'al transformer-to the grid of the tube-toenergize the tube-when the arma ture isin onepredetermined relation tothe transformer'at which the gridbias isbalanced, a.relay in-ther:tubecircuit, asecond tube'iin said relay circuit, means for applying 'avariable negativegrid .bias1to the said second tube, means. forvconducting. the output of the.- differential transformer toxthegrid ofthe second. tube to energize the second tube when the armature is in asecond predetermined relation to the. transformed at which the grid bias:ofthe-:second-tubeis :bal. anoedgand; a second relay, in the secondtube circuit,--said-circuit arranged tox-maintai-n the grid biason bothsaid .tubesand to prevent either tube fromtfiringgwhenrthe armature: isin .athird pree determined relation to the transformer between the:first;-and the second mentioned predetermined positions, atwhich the.outputuof thetransformer issubstantiallynull;

. 3,-.In .combination,., meansimovable' with the change of. conditionof. a conditionedcdevice ,as a function of such change, a,difierentialtrans: former, an I. armature imovablenwith. said. meansrelative-c to. saiddi'iferentialf transformer... saidtransformerrarranged. to. have anioutput .'succes-. sivelyofla voltageof one phase,.of fnulliivoltage, and a. voltage rofphase..substantiallylopposite to the. firstmentionedipli'ase asthe'armature passes relatively. to. the-transformer. from one relativeposition to anothena relay cir'cuit'includihg two tubes, means. forimpressing a variable grid bias on. each of 'the' tubes,,.meansimpressing the out put I of the differential transformer on the" respective gridsiof the tubes; so .arran'gedf'that'only one. tuberespondsto an outputbfone'phase while the other tube'respondsonly'to'the output of said'cpposite: phase; relays. in the respectivecoupled-with the respective relays-to betselec tively. and alternately,controlled in accordance with the energization of itsrespectivetubew 4.A trigger action phase-sensitive relay circuit,- comprising. a. powertransformer, connections-to.

theprimary-of said. transformer for :connection to a sourceof A. .C.voltage a signaltransfer-men, a multi-element gas tube, apotentiometenga, relay,;circuit connections joining; the cathodeiandanodeof said .tube. with thei secondaryofthei power transformerflandsaid relay, to actuatethe relay when thetube firesg. circuitconnections. coupling. the grid of the tube, .the.-secondary.-of-. thesignal transformer, themovable armiof the potentiometer and the'cathodeof the tube, means;- forimpressing a negative gridbias on thegrid.cathode circuit of the. tube throughsaidzpotene tiometer variable withthe setting of therarm thereof, .and means. for impressing a signal. oi

variable amplitude on the. primary. of the-signal. transiormer, which isinstantaneously substana tiallyin-phase or oppositelyout of phase-withthe voltage on the primary of=thepower transformer, whereby with .-a-.signal. of predetermined amplie tudeand ofphase opposite tothat of:the-nega! tive gridbias inthe secondary iofthesignalfltranse former saidgrid bias overcome and the tube .is fired.

5. -A trigger action phase-sensitiveorelay,circuit comprising a powertransformer. havingi.a.plu= rality of secondaries and a signaltransformer, connections to the primary of the powertransformer. for asource of A.. CLvoltage, aimulti-ielement gas tube, a potentiometerh'avinga movable arm, a phase-sensitive relay, .circuit ,con.-. nectionsplacing. the relay and a secondaryof the. power transformer in thecathod'e-anodecircuit of the tube to energize the relay. when the tube yfires, circuit connections to the potentiometer,

the cathode of the tube, andfrom the arm of the potentiometer through asecondary of the signal transformer and. to a secondary. of said'powertransformerwfor impressinga bias on the grid of said tube variable witharm relative movement; a. signal device,.circuit connections from asec-. ondary. ofrsaid. power transformer to the signal device forimpressinga signal on the secondary of said'signal transformersubstantiallyin phase with. or..of.v the opposite phase. from the phaseof the said cathode-anode circuitand said negative grid bias.respectively, whereby a signal impressed on the secondary of saidsignal trans former of. amplitude of predetermined value and of phaseopposite ..to that of .the grid .b'ias over' comes the bias and firesthe tube andactuates therelay.

WILLIAM.DL MAC'GEIORGEII REFERENCES CITED The. following referencessareof record inthe file of thispatent or the original patent:

UNITED STATES. PATENTS.

()"B-rien" June 1, 1948

